Apparatus for molding corrugated asbestos-cement sheets



Feb. 9, 1954 J, SEGRE 2,668,574

APPARATUS FOR MOLDING CORRUGATED ASBESTOS-CEMENT SHEETS Filed Feb. 7, 1952 2 Sheets-Sheet 2 Fi ll.

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1121. EL JAMES SEGRE i BY 4 ATTORNEY v Patented Feb. 9, 1954 UNI'I'IE`.-'l) FOFFEICLE -APPARA'rUsEon iii/[omino CORRUGATED -AsBEsfr-osoEMENfr SHEETS 4 Claims.

This invention is concerned with a processfand apparatus for molding corrugatedi'ashestosecementfsheets, i. e.sheets having"alternatelparallel ridges and grooves. More particularly, fmy inve'ntion pertains Itofrnoiding platensfor use lin'lthe .manufacture of corrugated asbestos-cement sheets andltoa vmethod-ofemployingsuchplatens.

Specicaily, my invention constitutes-animprovement 'of .la Ycurrent method 'for inakiirgV corru'gated :asbestos-'cement sheets pursuant to lwhich :Ia -fiat sheet 'of asbestos-cement, fobtained by any standard process, vas ifor example that shown :in United States Letters Patent v'No. 2,503,466, issued April 11, 1950 to William-Bernard et al. for Apparatus ifor Manufacturing Cement Asbestos Board, is' laid, 'While 'still '.plastic, i. -e. damp, on a'molding platen,vthe"profl1e ofiwhose top surface is the same' rasthe .desired proiile for the bottom surface of the corrugatedvsh'eet. Thesheeti's :forced against-.the platen in a forming 'operation which can fbe"practiced fby hand or machine, the latter -being Iexempliiied, 'fo'rinstance, by United "St'ates `Letters -VPatent No. 1;868;6451t'o "Scheeders-Van-Kerchovegissued July 26, 1932 for Apparatus lfor SimuItan'eous1y1Corf rugating and Trimming Sheets of-LAsbestos-Gementy 'fand "the like fin fa Plastic fC'onditon, and No. 12,210,985 to 'Ma'gnBLIiL issilodAilglISt 213; 1940 for AMethod for Corrugating 1 Sheets. v"The imolding 'platen andthe supe'riinposed formed plastic asbestos-cement vsheet are transferred 'to a drying sp'ace 'Where Ethe associated"platensfan'dfsheets are stacked' ont'op of ione another' itc/conserve room. The sheets are permitted to stand'iitil the icement `has :set and the 'sheets' are`dry' -and rigid. Thereupon the i'p1atens1and-sheets =are removed from fthe stack, Athe sheets separated from th'e 2platone 'and the lpl'ate'n's cleaned for 'subsequentuse At present, moldingplatens areabricated'ffrom sheet metal, e. fg. sheet-steel, 'the 'sheet ineta'l' being 'Tof uniform 'thickness 'and Vbeing E'shaped 'from the=at, ie. ig. byv pressing or rolling,tofprcvide a top `'surface 'whose p'roiile #matches thehesired p'role of the lbotto'msiirface o'f thel'corrugated asbestos-'cement sheet. Because vof the -iin'iiorzn and substantialthickness of ffiatasbestos-'cement sheets, th'e top rsurface of fa lcor'rii'gated "sheet made therefrom :has afprole Whichis'ianappreci'able mismatch vof 'theP-prle fof the bottom surface of the corrugated sheet, Lvandtherefore, of the profile' ofitheltopsrface of 'fthe 4corrugated platen. Moreover, becausethe sh'eet-imetalplaten also has lan 'fappr'eciable'iand uniform 4"thitvkness, the prciiie'iofflthe bottomsuface offthe'fplaten .2 isfsubstantially different from the profile ofthe top surface of the 'molded asbestos-cementfsheet. so'fhat 'the vlorofile 'of the'top 'of the sheet is` an even Lvvorse mismatch of the prole of 'the ybott'omfof'theplaten.

f'Ac'cord'ingly, when, in accordance with-'current practice,v corrugated platens and sheets are stacked for drying, the bottom of leach y`platen does lnctn'est snugly Iinto thetop 'of the underlying sh'eet so that the pressure fonthe :damp asbestos-cement sheets is highly 'irregular fduring drying. There is -no fpressure :between fthe sheets and-pl'atens at the'tops lothe'ridgesiand the lbottom's or the grooves f/(indeed there y'is vvva space between the sheetsand `rlolatens atfthese regions) and all pressure is concentrated -at-the slanting 4walls 'joining' thei/ri'dges 'and grooves. This results Vin several disadvantages :Well known to skilled workers fin "the art as', for example, non-uniform thickness, density, strength and' appear'allce. It is an 'object of -my invention to l'provi'de a method 'and'apparatus i of the vcharacter described which overcomes lthese disadvantages. llli/lore specifically, fitis an objectof l'my invention Ito kprovide la method and apparatus of fthe character described vwhich willfproduce -a vrcorrugated asbestos-.reculent sheet of uniform thick'- ness, density, Ystrength*and vsurface appearance. lIt is "a -further "object 4of l'my `invention fto' :provide amethod'and apparatus for manufacturing a `corrugated asbestos-*cement sheetfwhich has been compacted Ldurin'g -drying ywhereby Itov iincrea'seits density and strength, 'Without/howeverI losing uniformity 4of vthickness or any other desirable qualities.

Other Iobjects of fmy invention :Will part fbe obvious l"and in A1part'will be pointed fout V"hereinafter. r`'My @invention faccordingly consists 'in fthe ifeatures o'f construction, combinations Afoi elements -arran'g'eme'nts of partsvi'and :series :of stepsuwh'ich willslbe rexemplined y. in ithe :construction :fand method hereinafter "described `and vof 'which the scope-ier application will be indicated rinathenap- .penned iclaims.

In the accompanying draw-ings in .whichfare shown .various 'possible embodiments kof .my Linvention,

Fig. I1 is fa sectional view through astack'fof corrugated asbestos-cement sheets Sand =conven tional lplaten's, :the i 'same being 'taken transverse to :thealength-'ofl the fcorrugations 1: Fig. i2 is fa sectional 'view 'staken :substantially Fig. 3 is a View similar to Fig. l, but showing platens constructed in accordance with the present invention;

Fig. 4 is a sectional view taken substantially along the line 4 4 of Fig. 3;

Fig. =5 is a transverse sectional View through a platen of my invention and indicating certain critical dimensions;

Fig. 6 is a fragmentary transverse sectional view through a forming machine which is conventional save for platens embodying my invention;

Fig. '7 is a sectional view taken substantially along the line 1--1 of Fig. 6;

Fig. 8 is an end view of a press being used with my platens during a drying operation; and

Fig. 9 is a transverse sectional view through a corrugated asbestos-cement sheet which has been made with the aid of my platens. l

Referring now in detail to the drawings, and more particularly to Figs. 1 and 2, the reference numeral I0 denotes a corrugated sheet metal platen of conventional contour, that is to say, a standard platen which does not embody my invention. Said platen is manufactured, as by pressing and rolling, from fiat pieces of sheet metal of uniform thickness. In accordance with custom, the ridges l2 and grooves i4 are of substantially the same shape, that is to say, the radius of curvature of the ridges is substantially the same as the radius of curvature of the grooves. The profile of the platen constitutes circular arcs joined by straight slanting walls i6. All of the ridges and grooves are of the same height. It will be understood that the angular length of the circular arcs, the radii of said arcs and the length and inclination of the sloping walls may vary, although once a given set of such dimensions has been selected there is a strong tendency to retain the same due to the large investment in platens.

As noted above, when a platen of this construction is employed, a still damp, plastic, flat asbestos-cement sheet is placed thereon and is formed to follow the top surface of the platen, that is to say, the plastic sheet is forced against the platen so that the profile of its bottom surface exactly matches the profile of the top surface of the platen. However, the profile of the top surface of the sheet will not match the profile of the bottom surface of an overlying platen. The radii of curvatures and the centers of the circular arcs are such that there is a crescent space I8 between the top of each ridge in a sheet and the bottom of each groove in an overlying platen. Similarly there is a crescent space 2D between the bottom of each groove in a sheet and the top of each ridge in an overlying platen. Accordingly, each platen but the lowermost rests on the underlying corrugated sheet only along the sloping walls I6 joining the circular arcs, the area of contact being indicated in Fig. 1 by the reference numeral 22. All pressure is concentrated along this region so that this part of the corrugated sheet becomes thinner and more compact than the remainder thereof and often develops cracks. Moreover, due to this localized area of contact it is not practical to subject a stack of said platens and sheets to an external, e. g. machine, pressure.

The present invention obviates the foregoing drawback by providing a platen 24 of unique shape which is such that the upper surface of the platen consists of a series of ridges and grooves that exactly match the desired undersurface of a corrugated sheet and the undersurface of the platen consists of a differently shaped series of ridges and grooves that exactly match the desired A on the same surface of the sheet are of different diameter, the radius of curvature of the upwardly convex arcs (grooves) on the bottom surface of the sheet being less than that of the upwardly concave arcs (ridges) on said surface and the y radius of curvature of the upwardly concave arcs (grooves) on the top surface exceeding those of the upwardly convex arcs (ridges) on said surface.

More specifically, I achieve my invention by providing a corrugated platen of varying thickness. Said platen is desirably manufactured by a process which does not depend upon changing the shape of sheet material of uniform thickness but, rather, by a process which enables an object of varying thickness to be formed. For example, the platen can be made by forging or by molding, the latter preferably being used. Conveniently, the material of the platen may be a synthetic plastic so that the platen can be fabricated, for instance, by die-molding, e. g. low pressure or flash molding.

In order for a platen embodying my invention to obtain the exactly matching, i. e. nesting t with a corrugated sheet in the manner hereinabove described, the platen is specially shaped a best illustrated in Fig. 5.

The top surface of said platen has a transverse prole consisting of a series of upwardly convex circular arcs 34 of the same radius of curvature 36, all of said arcs heilig tangent to a single straight line 33. The radius 36 at the center 40 of each arc is perpendicular to said common tangential line.

The transverse profile top surface of theplaten also includes a series of upwardly concave circular arcs 42, all having the same radius 44' of curvature and all being tangent to a single straight line 46 parallel to the line 38. The radius 44 at the center 48 of each upwardly concave arc is perpendicular to the common tangential line 46.

The arcs of the two series alternate, that is to say, there is first an arc of one series and then one of another, e. g. first an upwardly convex arc 34, then an upwardly concave arc 42, then an'- other upwardly convex arc, etc. All the arcs are of the same angular length 2a.

The transverse prole of the top surface of the platen further includes straight lines 49 joining the ends of adjacent arcs, each said line being a common tangent to the arcs at their ends.

The bottom surface has a transverse profile consisting of a series of upwardly convex circular arcs 50 of the same radius of curvature 52, all of the arcs being tangent to a single straight line Sil-parallel tothe line 38. The radius 52 at the center 56 of each arc is perpendicular to the tangent line 54.

The transverse prole of the bottom surface of the platen further includes a series of upwardly concave circular arcs 58 of the same radius of curvature 60, all of said arcs being tangent to a single straight line 162 1paralleltoztlrellinel 38. The .radius 60 l.attlie .center 54 of reach "upwardly concave arc is' perpendicular to :the tangent #line 62.

The arcs-150:, 58 o'fithe two .series alternate, e. g. .there is nrstan upwardly'fcenvex arcr .and .then an upwardly Aconcafve are `58, .then an upwardly convex arc; etc. Theiangular lengths yof all the arcs 1511.-, .53' are lthe :same 'andare the same as those of the arcs 34, l2 ofthe transverse prole ofthe top surface.

The "transverse profiley of l the bottom surface also includes :straight lines 6 tangentially 'joining the ends of adjacent arcs and pa-rallelzto the lines 49.

Each upwardly convex arc at oiythe. vbottom transverse pron-legis paired with an .upwardly convex arc 313 :ofthe top transverse prole, and each upwardly concave a-rc .'58 ofthe -bottom transverse proleis ,paired with an upwardly concave arc t2 of the -top transverse profile. The bottom arc of each vpair is directly beneath and of the same langular length as the toparc of .that pair and the centers of each pair or arcs lie in a line perpendicular to the .tangential .lines 33, t5, 54, 62.

The length of the radii of the various arcs are critically interrelated in accordance with my invention. Thus the radius 36 of every upwardly convex arcr 3'4 of the -top transverse prole is shorter by S than the radius 52 of the matching upwardly convex Aarc di] ofA the bottom transverse profile where S is the thickness of the molded asbestos-cementsheet rllhe radius ifi or every upwardly concave arc 42 .of the top transverse proiile is longer by S than the radius 50 of the matching upwardly concave arc 53 oi the bottom transverse prole.

In addition to the critical interrelationship of the lengths of the radii, the centers about which the radii are described are critically interrelated. rihe center about which the radius of each arc 34, 42 of the top transverse prei-lle is described is P-i-S above the center about which the radius of the matching arc 50, 58 of the bottom transverse profile is described where P is the thickness of the platen at the centers 40, 48, 56, t4 of the matching upwardly convex and concave arcs.

When a plurality of platens such as described above are stacked with the crowns of the ridges and bases of the groves spaced vertically apart a predetermined distance equal to S the entire space between two adjacent platens will be of the same uniform thickness S.

By way of example and without in any manner limiting the invention I have set forth below typical values for the various dimensions of a platen constructed in accordance with my invention where S is six millimeters:

The radius 36 is forty-four millimeters. The radius 44 is fifty-one millimeters. The radius 52 is fty millimeters. The radius 60 is forty-iive millimeters. The distance between lines 38 and 46 is nity-seven millimeters. The thickness P of the platen at the centers of the circular arcs is six millimeters. The distance between the centers of the two radii for matching pair of arcs (P-i-S) is twelve millimeters. The distance between the center of a pair of matching convex arcs and a pair of matching concave arcs, i. e. the distance M2 from the center of a ridge to the center of a groove in a direction transversely of the sheet (for example along the line 38) is eighty-eight point ve millimeters. The length of all the circular arcs is 94. The perpendicular distance between a pair of lines 49, 66 tangen- 6 tiallyjoining'theaends .of circular arcsffisitwo point two millimeters.

In carrying out the methodofr invention ze. flat asbestos-cement 'sheet `2 formed any conventional `mannerfsuch that the. thicknesseof the sheet is uniform. .Before the :sheet: iiasflhad a` chance to seti, `itha-t :is .to say.- while- :it 4is :still 'damp 'and therefore pliable,and'r preferably @very shortly after. .it has come out rof the' sheet-:making mach-ine, the sheet :is placed upon-a -fplatenfd embodying .my invention and of 'the construction above described. Qptionallmthe platen' may be supported on a block .-Bl Whose uppersur-face is shaped to matchLv thefbottom.- surface of the platen. The sheet is vforced-finto the grooves .of the platen in accordance .with any. suitablemethod. For this pur.pose,.for instance, I may provide a plurality of rollers, 10.12, .14. These rollers may be depressed .against Kthe sheetin registry with grooves thereby causing-.the undersurfaceof the sheet. to match. .theupper surface Y-ofthe platen. The rollerscan .be manipulatedfby. hand or by machine, an vexample of .the `latter .being disclosed in the .aforesaid Magnani patent.

Next, the platen with .its .superimposed .corrugated asbestos-cement sheet is placedon the anvil l of a press' 13. Optionally, the anvil may .have its v.upper .surface corrugated. vto .match .the .bottom surface of the platen.V Thereafter. another platen with a super-imposed .cor1tugated...asbe`stoscement sheet is placedonthe iirst platen-sheet pair and pair after pairV .of platensandsheets superimposed thereon to forma stack .800i such pairs on the anvil. AIt Will .be observed that .due to the peculiar .congurationbt the platen pursuant to my invention, the pressure exerted on any given sheet by the superimposed platen is uniform throughout the entire surface thereof. By virtue of this unique feature the stack can be compressed by bringing down the head 82 of the press and any desired amount of pressure can be exerted without noticeably deforming the resulting corrugated sheet. The uppermost sheet is covered by a bare platen and, optionally, the bottom surface of the head 82 is corrugated to match the top of said platen.

It thus will be seen that I have provided a process and apparatus for molding corrugated asbestos-cement sheets which achieve the several objects of my invention and meet the conditions of practical use.

As various possible embodiments might be made of the above invention and as various changes might be made in the embodiment above set forth, it is to be understood that all matter and steps herein described, or shown in the accompanying drawings, are to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. For use in molding corrugated asbestoscement sheets of uniform thickness from a at plastic asbestos-cement sheet of uniform thickness, a one-piece platen having a top transverse prole constituting a series of upwardly convex circular arcs all having the same radius of curvature and being tangent to a single straight line, the radius at the center of each arc being perpendicular to said line, said top transverse prole also constituting a series of upwardly concave circular arcs all having the same radius of curvature and being tangent to a second single straight line, the radius at the center of each upwardly concave arc being perpendicular to said second tangent line, the arcs of'the two series alternating, the top 'transverseproile further constituting a group of straight lines joining the ends of adjacent arcs and tangent to the ends thereof, the bottom transverse profile constituting a series of upwardly convex circular arcs all having the same radius of curvature and being tangent to a third single straight line, the radius at the center of each upwardly convex circular arc of the bottom transverse prole being perpendicular to said third tangent line, the bottom transverse profile further constituting a series of upwardly concave circular arcs all having the same radius of curvature and being tangent to a. fourth single straight line, the radius at the center of each upwardly concave arc of the bottom transverse profile being perpendicular to the fourth tangent line, all of said tangent lines being parallel to one another, the arcs of the two series in the bottom transverse profile alternating, the bottom transverse prolle also constituting a group of straight lines tangentially joining the ends of adjacent arcs and parallel to the group of lines in the top transverse profile which tangentially join the ends of adjacent arcs therein, each upwardly convex arc of the bottom transverse prole being paired with an upwardlyr convex arc of the top transverse profile and each upwardly concave arc of the bottom transverse profile being paired with an upwardly concave arc of the top transverse prole, the bottom arc of each pair being directly beneath and of the same angular length as the top arc of that pair and the centers of each pair of arcs lying in a line perpendicular to the tangential lines, the radius of every upwardly convex aro of the top transverse prole being S shorter than the radius of the matching upwardly convex arc of the bottom transverse proiile where S is the thickness of the molded asbestos-cement sheet, the radius of every upwardly concave arc of the top transverse profile being S longer than the radius of the matching upwardly concave arc of the bottom transverse profile, the center about which the radius of every arc of the top transverse profile is described being P-l-S above the center about which the radius of the matching arc of the bottom transverse profile is described where P is the thickness of the platen at the centers of the matching arcs.

2. A platen as set forth in claim 1 wherein all of the arcs are of the same angular length.

3. A platen as set forth in claim 2 wherein the angular length of the arcs is about 45.

4. A platen as set forth in claim 3 wherein the radii of the upwardly convex circular arcs of the top transverse profile are substantially equal to the radii of the upwardly concave circular arcs of the bottom transverse profile and the radii of the upwardly convex circular arcs of the bottom transverse profile are substantially equal to the radii of the upwardly concave circular arcs of the top transverse prole.

JAMES SEGRE.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,283,630 Bean et al Nov. 5, 1918 1,794,435 Barth Mar. 3, 1931 

